Cadmium plating



United States Patent CADMKUM PLATING John B. Winters, Westlnke, Ohio No Drawing. Application December 14, 1956 Serial No. 628,237

21 Claims. (Cl. 204-50) This invention relates to the electrodeposition of cadmium and is particularly directed to plating bath com positions from which bright, mirror-like cadmium deposits are plated, consisting of cadmium cyanide baths characterized by containing in solution a N,N,N ,N tetrakis-(hydroxy alkyl) ethylene diamine; and to compositions of matter containing such compounds for use as cadmium cyanide plating bath addition agents. I

It is an object of this invention to provide cadmium cyanide plating bath compositions containing new and novel addition agents for producing bright, lustrous, mirtor-like cadmium electro-deposits, direct from the platare particularly effective in producing bright, lustrous,

mirror-like cadmium deposits from cyanide baths containing one or more of these novel brighteners, both alone and in combination with other materials that act in a synergetic manner, as hereinafter explained.

Mynew and novel cadmium cyanide plating bath addition agents,a's this class of compounds will hereinafter be referred to, may be described as consisting of totally hydroxyalkylated alkylene diamines having the general structural formula A as follows:

7 110-11 R -OH I N.R.N

v (A) HO-R R-OH' intwhich Rand R are alkyl radicals containing from 2 to 4 carbon atoms. i i

As a example of one specific compound of this type that hasbeen found to .be particularly efiective, I may cite the one in which R is a propylgroup and R7 is an ethylene group. it is designated as N,N,N,N-tetrakis(2- hydroxy propyl) ethylene diamine; that is," totally hydroxylated ethylene diamine,"and has the following structural formula, B: T

v I CH3 A group of compounds suitablefor the present purpose and similar to the compound shown in Formula Bis illustrated by the compoundinwhich one of the R radicals is an ethyl group, and the remaining three R radicals are propyl groups; that is, monohydroxyethyl trihydroxy propyl ethylene diamine, as illustrated in the following formula, C;

Other members of this group are like Formula C except that one, two or all three of the remaining R groups are hydrcxyethyl groups; that is dihydroxyethyl dihydroxy propyl, tr'ihydro'xyethyl monohydroxy propyl, and totally hydroxyethylated, ethylene diamine, respectively.

Another group of compounds suitable for the present purpose and having the structure of general Formula A is illustrated in Formula D in which one of the R radicals is hydroxybutyl; that is, monohydroxybutyl trihydroxy propyl, ethylene diamine:

CH3 CH3 HO-(lH-CHrCH} om-dn-on N-CHzCHg-N HO-CHCH2 CHr-GH-OH (D) i Hs Ha Other members of this group are like Formula D except that one, two or all three of the remaining R radicals are hydroxy butyl groups.

Still other groups of compounds which are suitable for the present purpose and similar to those of the abovestated general Formula A are the groups in which the R may be either propylene or butylene. Examples of these types of compounds are illustrated by the following general structural formulae:

The vforegoing propylene and butylenecompounds may bepreparedas follows: (1) Chlorinate propylene or propane to l-dichloro propylene propylene amine and butylene amine types may be hydroxyethyl, hydroxypropyl or hydroxy butyl, and any combination of two or more of these hydroxy groups.

The bath solubility of anyof the foregoing compounds is important since enough of;the.material 'must' dissolve in the bath to be effective. In the case of the above-mentioned compoundin which all four R radicals are hydroxypropyl radicals. and theradical R iisj ethylene,

the preferred amount to use in the cadmium cyanide platingbath is about 0.5 gram per liter although some efiectdsproducedwith as little as. 0.1 gram per" liter, while 1 gram perliter can be used without illeffects.

Similar amounts of each of the otherabove-mentioned compounds may likewise be usedin cadmium cyanide plating bathsiwithsome noticeable efiectrin-eachrinstance.

While my novel cadmium cyanide plating bath addition agents are effective in anyoperable cadmium cyanide plating solution, I prefer to use a bathhavin'g the general formula, 1 Grams per :liter Sodium ;cyanide,tNaCN v12o Cadmium. oxide, CdO

My novel cadmium cyanide platingbath addition agents have numerous advantages over other such materials now being 'used commercially. T hey are not only brighteners, butalso anti-pit agents, so that no secondary materials are needed to prevent pitting of deposits. Another advantage isthat my novel brighteners are definite chemical compounds whose composition, canbe controlled and duplicated, in distinction to those brighteners which contain organic. matter of unknown composition. Still on the cathodes, so as to keep. theanode surfaces b ight and clean. They actito promote uniformanodecorrosion and preventselective attack at the crystal boundaries,

which results in fine metallic, particles being dispersedin the .bath, which migrate to the cathode, thereby producing roughideposits.

Still another advantageis .thefrhigh, degree ofsstability of my novel cadmium plating addition agents in the alkaline cadmium cyanide plating bath under operating conditions, whichmakes for economy, since only the brightener lost by bath dragout needs to lee-replaced.

While my novel I cadmium cyanide plating bath addition agents are effective whenusedalone in cadmium cyanide plating baths, it is expedient for some purposes to combine them with other materials; that act synergetically to produce certain desirable resultstunder some conditions. For example, they may be used in combination with certain colloidal vmaterialstto improve the -brightness of depositaandcoverage in the low current density areas on irregularly shaped objects, particularlytin ,barrel platingsolutions. *As examples ofcolloidalmaterials suitable for use with my novel cadmium cyanideg'p lating bath addition agents, I may cite'gelatin, "peptonej and hydroxy ethyl cellulose, the last named being preferred. These materials are added to the plating bath to produce concentrations of frorn aboutflllto 1 gram per liter, but in general not greater than the concentration of my novel; addition agent in the bath at the time. r

a In order to broaden'the brightplatingcurrentxdensity range, particularlyin .the. higher ranges, I have found it expedient to add alsoluble nickel or; cobalt isaltas taught imU. S. Patent, 1,681,509.; Any bathsolubleicompound of :nickeltmay be usedto produce .a: bath conoentrationof approximately 0.02 to 0.2 gram of nickel. pen-liter," but in general the, nickel concentration: should, not be greater thamabout one-fifth the .concentrationofmy novelsaddition ,agentin the bath at ;the.tirne. I Y

It is apparent from 1 the foregoing.- that .nndersceriain conditions it will be; advantageous :to .use:.mixturesr-oftzone or ,more of ,my novel brighteners with a colloidalnnaterial. -Asz timexample ofusuch 1a mixture cthat llihave found=tosbeefiective is a mixture of N,'N,N*,N ;=tet1"akis v a 4 '(Z-hydroxy ethyl) ethylene diamine one part and hydroxy ethyl' cellulose one part, themixture being added to the I have found that .mixture addition. agents can be I compounded so as to produce superior results over the wide range of operating conditions encountered with commercial cadmium cyanide plating baths. Such mixtures are made by mixing one or more of my novel.addition agents with a colloidal material and a bath soluble nickel compound. For convenience, such addition agents are best compounded in the form of a solution portions of which can be added to a cadmium cyanide platingbatl'l. As an example of one such solution that'I found to produce particularly good results, I cite the following formulation:

Grams per liter N,N,N, ,N tetrakis (2-hydroxy'propyl) ethylene diamine .20 Hydroxy ethyl cellulose 10 NiSO -7H O i 10 'This mixed' addition agent solution 'is then added'to a cadmium cyanide plating bath inthe proportion of about 18 cc. of addition agent solution per liter of plating bath,'or about 250 fluid ounces of mixed addition agent solution per 100 gallons of plating bath.

Example 1 A -general formula for such mixed addition agent form: ulationscoming within the scoperof my invention would be:

. Parts N,N,N ,N :tetrakis, (hydroxy alkyl) ethylenedi- .amine -20 Hydroxyethyhcellulose :10

Water 950 Other. compounds which come within the scope of my invention andhave been found to give satisfactory results are illustrated in Examples Nos. 2 and 3:

"Example 2 Parts Monohydroxyethyl trihydroxypropyl ethylene diamine 18 Peptone l2 Water 954 Example 3 Dihydroxye'thyl,dihydroxypropylethylene diamine-.. l6

Gelatin '13 NiSO '7H- O y 14 Water .957

This application is a continuation-in-partof my co pending application Serial No. 481,969, filed January 14, 1955, now abandoned.

Whilethednvention has beendescribed as embodied in concrete form and as operating in a specific manner in accordance .with the provisions ofthepatentastatutes,

- I claim:

taining a totally'hydror yalkyiated ethylene diamine hav ingthe formula HO-R HO-R R-OH in which each R is an alkyl radical containing from 2 to 4 carbon atoms, in a concentration of about 0.1 to about 1 gram per liter.

2. A cadmium cyanide plating bath composition containing a totally hydroxyalkylated ethylene diamine having the formula HO-R R-OH HO-R R-OH where each R is an alkyl radical containing from 2 to 4 carbon atoms, in a concentration from about 0.1 to about 1 gram'per liter and a colloid selected from the group consisting of gelatin, peptone, and hydroxy ethyl cellulose in a concentration of about 0.1 to about 1 gram per liter.

3. A cadmium cyanide plating bath compositioncontaining a totally hydroxyalkylated ethylene diamine having the formula HOR R-OH N-CHz-CHz-N HOR R-OH where each R is an alkyl radical containing from 2 to 4 carbon atoms, in a concentration of about 0.1 to 1 gram per liter and nickel in bath soluble form in a concentration of about 0.02 to 0.2 gram per liter..

4. A cadmium cyanide plating bath composition containing a totally hydroxyalkylated ethylene diamine having the formula where each R is an alkyl radical containing from 2 to 4 carbon atoms, 'and a colloid selected from thegroup consisting. of gelatin, peptone, and hydroxyethyl cellulose, each being in concentration of about 0.1 to 1 gram per liter, and nickel in bath soluble form in a concentration of about 0.02 to 0.2 gram per liter.

5. A cadmium cyanide plating bath composition containing N,N,N ,N -tetrakis (2-hydroxy propyl) ethylene diamine in a concentration of about 0.1 to 1 gram per liter.

6. A cadmium cyanide plating bath composition containing N,N,N ,N -tetrakis (2-hydroxy ethyl) ethylene diamine and a colloid selected from the group consisting of gelatin, peptone, and hydroxy ethyl cellulose, each in concentration of about 0.1 to 1 gram per liter.

7. A cadmium cyanide plating bath composition containing N,N,N ,N -tetrakis (Z-hydroxy butyl) ethylene diamine in a concentration of about 0.1 to 1 gram per liter and nickel in bath soluble form in concentration of about 0.02 to 0.2 gram per liter.

8. A cadmium cyanide plating bath composition containing N,N,N ,N -tetrakis (Z-hydroxy propyl) ethylene diamine and hydroxy ethyl cellulose, each in a concentration of about 0.1 to 1 gram per liter and nickel in bath soluble form in a concentration of about 0.02 to 0.2 gram per liter.

9. A composition of matter for use in cadmium cyanide electroplating baths containing totally hydroxyalkylated ethylene diamine in which all the alkyl substituents contain from 2 to 4 carbon atoms, a colloid selected from the group consisting of gelatin, peptone, and hydroxyethyl cellulose, and nickel in bath soluble form in proportions to each other effective when added to a cadmium cyanide plating bath to produce the bath composition of claim 4.

10. A liquid addition agent for use in cadmium cyanide electroplating baths containing in aqueous solution, N,N,N ,N -tctrakis (2-hydroxy propyl) ethylene diamine one part, hydroxy ethyl cellulose in amount equal to from about one-fifth part to one part, and nickel in the form of water soluble salt equivalent to nickel'from' about one-twenty-fifth part to one-fifth part.

11. A liquid addition agent for use in cadmium cyanide electroplating baths containing in aqueous solution, N,N,N ,N -tetrakis (2-hydroXy propyl) ethylene diamine one part and hydroxy ethyl cellulose one part, and nickel in the form of a water soluble compound in proportion of approximately one-fifth part of nickel.

12. A cadmium cyanide plating bath addition compo-- sition containing substantially equal parts of N,N,N ,N tetrakis (hydroxy propyl) ethylene diamine, a colloid selected from the group consisting of gelatin, peptone, and hydroxy ethyl cellulose, and nickel in bath soluble form.

13. A cadmium cyanide plating bath addition composition containing about one part of N,N,N ,N -tetrakis (Z-hydroxy propyl) ethylene diamine and between about one-fifth part and about one part. of hy-droxy ethyl cellulose.

14. A cadmium cyanide plating bath addition composition containing about one part of N,N,N ,N -tetrakis (Z-hydroxy propyl) ethylene diamine and between about one twenty-fifth part and about one part of nickel in the form of a water soluble salt.

15. A cadmium cyanide plating bath composition containing a totally hydroxyalkylated alkylene diamine having the formula HO-R R-OH in which each R and R is an alkyl radical containing from 2 to 4 carbon atoms, in a concentration of about 0.1 to about 1 gram per liter.

16. A cadmium cyanide plating bath composition containing a totally hydroxyalkylated alkylene diamine having the formula in which each R is an alkyl radical containing from 2 to 4 carbon atoms and R' is a propyl radical, in a concentration of about 0.1 to about 1 gram per liter.

17. A cadmium cyanide plating bath composition containing a totally hydroxyalkylated alkylene diamine having the formula HO-R \NR-N HO-R R-OH in which each R is an alkyl radical containing from 2 to 4 carbon atoms and R is a butyl radical, in a concentration of about 0.1 to about 1 gram per liter.

18. A cadmium cyanide plating bath composition containing a totally hydroxyalkylated alkylene diamine having the formula HO-R NR-N HO--R R-OH where each R and R is an alkyl radical containing from 2 to 4 carbon atoms, and a colloid selected from the group consisting of gelatin, peptone, and hydroxyethyl cellulose, each being in concentration of about 0.1 to 1 gram per liter, and nickel in bath soluble form in a concentration of about 0.02 to 0.2 gram per liter.

R-O H 7 .19. A composition of vmatter for use in cadmium-cyanide electroplating .baths containing atotally hydroxyalkylated .alky-lene diamine having theformula no-1 /R-OH' /N-R-N\ HO-R R-OH in which'each R and- R is an alkyl radical containing from 2 to 4 carbon atoms, acolloid selected from the group consisting of gelatin, peptone, and hydroxyethyl cellulose, and nickel in bath soluble form in proportions to each other eflfective when added to a cadmium cyanide plating bath to producethe: bath composition of claim 18.

20. A composition ofmatter for'use in cadmium cyanide electroplating baths containing a totally hydroxyalkylated alkyl'ene: diamine having the formula HO-R R--OH v in which each R is an alkyl radical containing from 2-to 4 carbon-atoms and R is a propyl radical, a colloid selected from the group consisting of gelatin, peptone and hydroxyethyl cellulose, each being in concentration of about 0.1 to 1 gram per liter, and nickel in bath soluble form in a concentration of about 0.02 to 0.2 gramc per liter.

.211. A composition of matter for use in cadmium cyanide electroplating baths containing a totally hydroxyalkylated alkylene diamine having the forrnula HO-R ROH N-R -N References Cited in the file of this patent FOREIGN PATENTS Germany Feb; 3, 1943 OTHER REFERENCES Sequestrene, Alrose Chemical Co., Providence, R. 1., July 25, 1952, page 28. 

15. A CADMIUM CYANIDE PLATING BATH COMPOSITION CONTAINING A TOTALLY HYDROXYALKYLATED ALKYLENE DIAMINE HAVING THE FORMULA 